How to Install Freon in a Monte Carlo

by Lee Sallings

Over time, the seals in the air conditioning system will leak small amounts of refrigerant until the system loses some of its cooling capacity. Adding freon to your Monte Carlo's air conditioning system will keep it operating at maximum cooling efficiency in the heat of the summer. The average home mechanic can complete this repair project in about an hour. Remember--if you are making a repair that will open the system, it is illegal to vent refrigerant into the atmosphere.

Attach the high-pressure (red) and low-pressure (blue) hoses to the service ports located on the aluminum air conditioning lines under the hood. In the Monte Carlo, the high-pressure port is located on the thin line that connects the condenser, located in front of the radiator to the evaporator under the dash. The low-pressure port is located on the side of the accumulator--the aluminum cylinder shaped part--attached to the passenger side of the firewall.

Start the engine and set the air conditioning controls to "Max" air conditioning and "Medium" blower speed. This provides the best temperature readings when the output temperature is measured. Allow the engine to run for a few minutes to stabilize the system pressures.

Attach a can of refrigerant to the can-tap attached to the service hose (yellow) in the center of the gauge set. Open the can of freon by turning the thumb-screw in to puncture the seal in the can and then out to open the can. With the engine running, open the blue valve on the gauge set to allow the freon to flow into the system. Close the valve when the can feels empty and allow the pressures to stabilize.

Read the a/c gauges on the set. The low-pressure gauge will read between 30 psi and 35 psi on an older system using R-12 refrigerant (freon) and between 35 psi and 40 psi on a newer system using R-134a refrigerant. The high-pressure gauge will read between 150 psi and 250 psi on the R-12 systems, or between 250 psi and 350 psi on the R-134a systems. Add additional cans of refrigerant as needed to reach these pressures.


  • check A properly functioning air conditioning system will have a minimum of 40 degrees difference between ambient air temperature and inside air temperature

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About the Author

Lee Sallings is a freelance writer from Fort Worth, Texas. Specializing in website content and design for the automobile enthusiast, he also has many years of experience in the auto repair industry. He has written Web content for eHow, and designed the website. He began his writing career developing and teaching automotive technical training programs.